Best Actions to Take When RO Chemical Cleaning Is Ineffective| Insights by AQUALITEK

If Chemical Cleaning Is Ineffective, What Should Be Done Next?

Chemical cleaning is the last defense before full membrane replacement. When it fails to restore performance, operators must respond quickly and correctly to avoid further damage, system downtime, and unnecessary costs.

Below are the best and most practical steps to take after an ineffective CIP cleaning.

1. Confirm the Cleaning Process Was Performed Correctly

Before assuming the membrane is irreversibly damaged, verify that the cleaning was done properly.

Check the following:

•Cleaning chemical type was correct (acidic for scale / alkaline for organic)

•Correct concentration was used

•Solution temperature was within recommended range (25–35°C)

•Proper circulation time (30–60 minutes)

•Soak time was included

•Adequate flushing after cleaning

If any step was missed, repeat the CIP correctly before replacing the membrane.

2. Analyze the Type of Fouling and Match the Chemical Again

Often, cleaning fails because the wrong chemical was chosen.

Common mismatch examples:

If alkaline cleaning failed, attempt an acid clean next (or vice versa).

3. Check Pretreatment System Status Immediately

If fouling returns quickly after cleaning, pretreatment failure is the real cause.

Inspect:

•SDI level (should be < 3-5)

•Turbidity (should be < 1 NTU)

•Cartridge filters

•Antiscalant dosage

•Activated carbon performance

•Softener function (if present)

Cleaning without fixing pretreatment failure is only temporary.

4. Perform a Membrane Autopsy (Sample Element) If Possible

If this is a large system:

•Remove one membrane element

•Open and visually inspect

•Check for scaling crystals, slime, oil, or oxidation damage

This helps you confirm whether:

•Membrane is recoverable

•Type of fouling present

•Replacement is unavoidable

5. Replace Only the Most Damaged Stage First

In many cases, the first-stage membranes are the most affected.

Rather than replacing the entire system at once:

•Replace stage 1 membranes first

•Monitor performance improvement

•Replace other stages only if required

This strategy reduces replacement cost significantly.

6. Consider a Performance or Energy Upgrade

If replacement is necessary, take it as an opportunity to upgrade:

•Use low-energy membranes

•Improve salt rejection

•Optimize system recovery

•Reduce operating power costs

This can offset the cost of replacement over time.

7. Implement Preventive Measures Immediately After Replacement

Once the new membranes are installed:

✅ Improve feedwater monitoring
✅ Upgrade pretreatment if needed
✅ Install automatic flushing
✅ Set differential pressure alarms
✅ Start routine trend analysis
✅ Schedule preventive cleanings

This prevents repeated failure.

Key Rule: When Is Replacement Mandatory?

The membrane must be replaced when one or more of the following exist:

•Flow recovery < 70% after cleaning

•Salt rejection recovery < 80%

•ΔP does not return to normal

•Signs of oxidation or biodegradation

•More than 2 unsuccessful cleanings in a row

At that point, replacement is more economical than continued cleaning.

Conclusion

When chemical cleaning is ineffective, do not repeat it blindly.

The best approach is:

1.Verify the cleaning procedure

2.Reevaluate the fouling type

3.Fix pretreatment problems

4.Inspect membrane condition

5.Replace only what is necessary

6.Upgrade and prevent future failure

This systematic strategy minimizes downtime, reduces cost, and protects long-term system performance.